Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $161.36   13.193%   $182.6482   $182.65   $182.65   $182.60  
  Purchase #2 $62.94   10.718%   $69.6859   $69.69   $69.70   $69.70  
  Purchase #3 $54.27   8.610%   $58.9426   $58.94   $58.95   $58.90  
  Purchase #4 $76.99   9.172%   $84.0515   $84.05   $84.05   $84.10  
  Purchase #5 $205.47   10.551%   $227.1491   $227.15   $227.15   $227.10  
  Purchase #6 $227.49   8.267%   $246.2966   $246.30   $246.30   $246.30  
  Purchase #7 $93.51   4.438%   $97.66   $97.66   $97.65   $97.70  
  7 purchase totals = $882.03       $966.4339   $966.44   $966.45   $966.40